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This article was published in 1963
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Respiratory Diseases in Fowls
B. SINKOVIC, V.M.D., Department of Veterinary Medicine, Rural Veterinary Centre, The University of Sydney, Camden
Until a few decades ago all diseases of the upper and lower respiratory tract in fowls were referred to as "roup." Fortunately this term has nearly disappeared, even from the dictionary of the poultry farmer, because these days we have a fairly clear-cut picture of the aetiology of avian respiratory diseases. There are, however, two viruses in chickens, namely Fahey-Crawley and CELO, whose significance in causing respiratory diseases under field conditions is not understood completely, but everything indicates that these are of rather negligible significance.
In spite of our present knowledge of the aetiology, the differential diagnosis of these diseases still represents the greatest challenge to the diagnostician, be it in field or laboratory. It a disease would manifest itself in its so-called "classical form" the work of the diagnostician would be rather easy. Unfortunately the text-book picture is not seen commonly, and our quite recent experience with Infectious Bronchitis, a disease thought to be exotic, and which may have been present for a number of years in this country, is an example which speaks in favour of the above statement.
The clinical manifestation in respiratory diseases, as in most others, may vary considerably, depending upon the virulence of the infective agent, or the severity of the causative factor, the age and resistance of birds, and the system of management.
Certain respiratory diseases will affect only the upper, some others only the lower, and some again may involve both the upper and the lower respiratory tract. The latter group includes the "true" respiratory diseases, and it is here where even an experienced eye often fails.
With the exception of fowls, other avian species are rarely subject to respiratory symptoms. In the following classification the diseases in these other species will be mentioned only for the purpose of assisting the field veterinarian. The diseases will be grouped according to their aetiology, namely those caused by faulty feeding and management, by helminths, fungi, bacteria and viruses. The emphasis will be laid only to some recent observations either in this, or some other country.
FEEDING & MANAGEMENT: Avitaminosis A, chilling, overheating and ammonia fumes irritation.
(a) Vitamin A deficiency: This may occasionally represent a problem to the diagnostician, particularly cases being characterised only by lachrymation. Sometimes it occurs concurrently with other respiratory diseases.
(b) The other three conditions usually are seen only in chickens during the brooding age. Respiratory symptoms are seen rarely in chilled or overheated birds, and ammonia fumes, which cause lachrymation, will be detected easily upon entering the brooder house, and the symptoms will disappear soon after the house is properly ventilated.
HELMINTHS
(a) Eyeworm (Oxyspirura mansoni): This parasite is present in Queensland and probably the North Coast of New South Wales. Heavy infestations are characterised by frothy or purulent ocular discharge and oedema of the conjunctiva.
(b) Fluke in Ducks (Thyphlocoelium cimbium): There is evidence of dyspnoea due to presence of the parasite in larynx and trachea.
(e) Gapeworm (Syngamus trachealis): This does not occur in Australia. It has been recorded in white-capped starlings of Africa in Adelaide Zoo.
FUNGI
Aspergillosis: Gasping and accelerated breathing may be present, but without gurgling. Occasionally there may be accumulation of cheesy material under the nictitating membrane.
BACTERIA
Pullorum Disease, Pasteurellosis, Infectious Coryza, Colibacillosis, Chronic Respiratory Disease (CRD), Infectious Sinusitis of turkeys and Sinusitis in ducks. For Pullorum Disease the same applies as for chilling or overheating.Pasteurella multocida: This organism is isolated occasionally from the respiratory tract of fowls affected with some other respiratory diseases. It is hard to estimate its significance because, usually when that particular respiratory disease is brought under control, there does not appear to be any trouble with fowl cholera. Following an acute outbreak of Pasteurellosis, some birds may develop rales, nasal and ocular discharge.
Infectious Coryza: It is impossible to estimate the incidence of this disease in Australia, as isolation of the causative organism Haemophilus gallinarum from the field cases is rather complicated and most of our diagnostic laboratories do not carry it out as a routine. No doubt certain outbreaks of coryza are misdiagnosed clinically as CRD and vice versa. The diagnosis is very often based upon a favourable response to sulphathiazole treatment. Some recent outbreaks in California have shown unusual features, such as accumulation of white cheesy material in the air-sacs, and the failure to respond to either sulphathiazole or antibiotics.
Colibacillosis: This condition has appeared only recently in New South Wales, mostly among broilers 6-10 weeks of age, and housed in poorly ventilated and overcrowded sheds. Some other stresses. able to lower the bird's vitality, appear to play an important part in increasing pathogenicity of otherwise non-pathogenic E. coli. This disease is fairly commonly associated with CRD. Dyspnoea and sneezing, without nasal and ocular discharges or facial swelling, are the common symptoms, and on post-mortem examination there is fibrinous pericarditis and hepatitis, and caseous air-sacculitis. Most outbreaks respond favourably to furazolidone.
Chronic Respiratory Disease (CRD): During the last few years many broiler growers have adopted the "all-in-all-out" system of rearing, and ever since, the economic importance of CRD has been on the decrease. There is also a tendency among the breeders to establish CRD-free flocks by simultaneous de-population and re-population. As an additional measure, some hatcheries in New South Wales have been experimenting with the dipping of eggs in erythromycin prior to incubation, to prevent egg-transmission of Mycoplasma gallisepticum. Vaccination has met with some success in the U.S.A.
On serology, most of our breeding and egg-producing establishments show a high percentage of reactors, although clinical manifestation of CRD may not be present.
Symptoms commonly seen are nasal and, sometimes, ocular discharge, tracheal rales and coughing, together with loss of weight and drop in egg production. Catarrhal exudate in the nasal passages and trachea is found on post-mortem examination and the air-sacs are clouded and covered, depending upon the severity and duration of the disease, and the presence of secondary invaders, with either catarrhal or caseous exudate.
Antibiotics are of some help, particularly streptomycin i/m, and, more recently, tylosin tartrate and erythromycin, both claimed to be specific for Mycoplasma gallisepticum.
Infectious Sinusitis of Turkeys: This is caused by the same organism as CRD in fowls. Serum slide agglutination, a useful serological flock test in fowls, is not as accurate with turkey sera.
In younger birds involvement of the upper respiratory tract (nasal and ocular discharge, sinusitis) is commonly seen, while in older birds the lower respiratory tract (dyspnoea, coughing, air sacculitis) is occasionally involved.
Control measures should be carried out along the same lines as with CRD.
Sinusitis in Ducks: The clinical picture is very similar to the infection of the upper respiratory tract with Mycoplasma gallisepticum in turkeys. Muscovies appear to be resistant. An organism of the Pasteurella group was isolated from the sinuses in every outbreak, but no attempt has been made to produce the disease artificially.
VIRUSES
Infectious Laryngo-Tracheitis (ILT), Infectious Bronchitis (IB), Fowl Pox and Neural Fowl Paralysis (Neural Lymphomatosis).
I.L.T.: During the last two years it has been observed that cases of Haemorrhagic Tracheitis, a common feature in outbreaks of I.L.T. in the Sydney metropolitan area in the past, are rarely seen these days. The mortality rate accordingly has been lower. The clinical picture in these sub-acute cases is similar to CRD, but the spread of the disease is more rapid. Outbreaks characterised only by lachrymation have been recorded recently in the U.S.A. With the rise of the broiler industry, the incidence of the disease in chickens during the brooding age has increased considerably.
In England agar gel diffusion test has been tried successfully as a cheap and fairly quick diagnostic aid. Tracheal exudate of suspected birds is used as antigen and tested with a known ILT hyperimmune serum.
A quick histopathological method for demonstration of the typical ILT intranuclear inclusion bodies in tracheal epithelium has been described in the U.S.A. This method, which takes less than three hours from the time of tissue collection until the sections are ready for examination, has been proved successful at Sydney University. As the inclusion bodies were present in most birds 48 to 96 hours post infection, it is recommended that several birds in the early stages of the disease be submitted to the diagnostic laboratories.
Feather follicle method of vaccination is usually adopted if the birds are less than three weeks of age.
Infectious Bronchitis (IB): During the last few months a virus has been isolated at New England University, Armidale, Veterinary Research Station, Glenfield and Sydney University, which shows many characteristics of the I.B. virus. The Armidale virus was isolated from chickens affected from the kidney breakdown complex, known as Uraemia, and the affected birds came from different parts of New South Wales. This virus causes mild sneezing and tracheal rales in chickens exposed to the infection 24 to 48 hours previously, and in adult hens there is also a drop in egg production, poor quality egg shell, and embryonic mortality in fertile eggs. Respiratory symptoms last only for a day or two, and after an apparently normal period of 3 to 4 days the birds develop nephrosis. The Glenfield virus produced the same respiratory symptoms in experimental chickens, but no nephrosis.
The Sera from birds which recovered after exposure to the Armidale virus neutralised the four classical strains of American IB virus. However, the American L.B. antisera did not neutralise the Armidale virus.
On the basis of symptomatology, lesions in chicken embryos, and the serology, it appears that I.B. is present in New South Wales. Further detailed experiments should clarify whether all strains in New South Wales are identical, and what is their relationship to the American virus.
Agar gel diffusion test has been used with success in the U.S.A. as a diagnostic aid.
Fowl Pox: The diphtheritic form of this disease causes respiratory distress, but in most cases it is not a problem to the diagnostician. The presence of cheesy pseudo-membranes firmly attached to the mucosa of the mouth and the larynx, and evidence of cutaneous pox lesions in some birds of the flock, clinch the diagnosis.
Neural Fowl Paralysis: Gasping and sneezing in odd birds without any catarrhal exudation is observed occasionally in birds affected with this disease. On post-mortem examination unilateral or bilateral, partial or complete swelling, and loss of cross-striation will be observed in the vagus nerves.